You set your stationary bike on a high 80-n friction-like resistive force and cycle for 30 min at a speed of 8.0 m/s . your body is 10% efficient at converting chemical energy in your body into mechanical work.

a.) what is your internal chemical energy change?

b.) how long must you bike to convert 3.8×105 j of chemical potential while staying at this speed? (this amount of energy equals the energy released by the body after eating three slices of bread.)